Compositions and processes for separation of bitumen from oil sand ores

ABSTRACT

Compositions and processes for separating bitumen from oil sands ore include contacting the oil sand ores with a composition including a carboxylate salt and/or acid and an aqueous liquid carrier. The carboxylate salt and/or acid is a C 1 -C 7  alkyl, and in one embodiment, is a monocarboxylate.

BACKGROUND

The present disclosure generally relates to processes for separating oilfrom oil sands.

Oil sands ore (also referred to as tar sands) are a combination of clay,sand, water, and oil-rich bitumen, which is chemically similar toconventional crude oil but has a higher density (i.e., a lower AmericanPetroleum Institute (API) gravity) and a much higher viscosity. Thetypical high grade ore contains about 11% by weight or more of bitumen,the rest being largely sand and clay fines. The bitumen in oil sands orecannot be pumped from the ground in its natural state, instead the oilsands are either surface mined or subjected to in situ mining processesto extract the bitumen, which is then refined into oil. In surfacemining, the oil sands ores are crushed and transported to an extractionplant where bitumen is separated from water and sand. In situ processingrefers to various methods used to recover deeply buried bitumendeposits. Cyclic steam stimulation (CSS) and steam-assisted gravitydrainage (SAGD) are in-situ recovery methods, which include thermalinjection through vertical or horizontal wells, solvent injection andcarbon dioxide methods. Other technologies are emerging such as pulsetechnology and vapor recovery extraction (VAPEX).

Current processes for extracting the oil-rich bitumen from oil sandsinclude a hot water flotation process. The hot water flotation processincludes many variations but generally begins with a conditioning step.In this step, the oil sands are vigorously mixed in relatively largetumblers or conditioning drums with hot water to break up large lumpsand form a slurry. A newer approach eliminates tumblers or conditioningdrums altogether. After the oil sand is crushed at the mine site, it ismixed with warm water and then moved by pipeline to the extractionplant. The piping system is called hydrotransport and is configured tocondition the oil sand while moving it to extraction. The water used forhydrotransport is generally cooler (but still heated) than in thetumblers or conditioning drums, further reducing energy costs.

To assist in the recovery of bitumen during conditioning, additives canbe added to the slurry. For example, a basic material such as sodiumhydroxide is oftentimes added in order to maintain the pH balance of theslurry slightly basic, in the range of 8.0 to 8.5. This has the effectof dispersing the oil sands and reduces the viscosity of the slurry,thereby reducing the particle size of the minerals in the oil sands. Theaddition of the basic material can also saponify natural surfactantswithin the oil sands. The natural surfactants are known to alter thesurface electric charges and interfacial tensions between the differentmaterials within the oil sand, thereby making separation less efficientand less effective. For example, it is believed that ionization ofsurface groups and adsorption of charged surfactants can cause increasedelectrostatic repulsion, which increases the disjoining pressure in theaqueous film separation of the bitumen and the solids.

Once conditioned, the slurry is screened to separate larger debris andthen fed to a separation vessel, where it is allowed to separate intothree layers. Additional hot water may be added. Gravity separation ofthe sand and rock from the slurry occurs allowing a portion of thebitumen to float to the top where it is concentrated and removed asbitumen froth. The froth typically contains 60% by weight bitumen, 30%by weight water and 10% by weight sand and clay fines. The larger sandparticles and rock settle to the bottom where it is then pumped intosettling basins commonly referred to as tailing pond. The intermediateportion is often referred to as the middlings, which is relativelyviscous and typically contains dispersed clay particles and some trappedbitumen which is not able to rise due to the viscosity. The middlings isthen exposed to froth flotation techniques to recover additional bitumenthat did not float to the top during gravity separation. After which itis passed to the tailings pond.

The bitumen froth is passed to a defrother where the froth is typicallyheated and broken to remove air. Naptha or a paraffinic solvent may beadded to cause a reduction in the density of the bitumen so as to permitcentrifugation as a means for separating the bitumen from the water andsolids.

It is recognized in the industry that sodium hydroxide should be used aslittle as possible in the hot water flotation process, having regard tothe need for controlling fines and extracting bitumen from poor ores.This is because sodium hydroxide addition increases the cost of thetreatment process. Also, it is known that sodium hydroxide seriouslydelays the settling rate of tailings (the mixture of minerals, clay andwater which is left over after extraction of the bitumen). Thisincreases the difficulty of managing the disposal of the tailings. Also,it is found that addition of sodium hydroxide beyond a certain optimumlevel for any particular ore does not increase bitumen production: infact, it may reduce it.

Although the role of sodium hydroxide in bitumen froth production is notwell understood, a few studies have linked it to the production ofnatural surfactants. It has been said that aged bitumen may be deficientin surfactants, and sodium hydroxide could cause some to be generated.However, this work has not led to any method of identifying bitumenwhich is lacking in such surfactants, or to any practical process oftreating such ores. Further, the amount of sodium hydroxide which issuggested in these articles for addition to high grade ore is low, beingabout 0.01 weight %.

While current processes are satisfactory for their intended purpose,there is an ongoing need to improve process efficiency especially as itrelates to oil sands of poor quality.

BRIEF SUMMARY

Disclosed herein compositions and processes for enhancing recovery ofbitumen from oil sands ore. In one embodiment, the composition comprisesat least one C₁-C₇ monocarboxylic acid salt and/or acid in an aqueousliquid carrier; and oil sands ore containing bitumen, wherein the atleast one C₁-C₇ monocarboxylic acid salt and/or acid is in an amounteffective to separate the oil sands into a froth phase, a middlingphase, and sand and rock phase.

A process for enhancing the efficiency of bitumen recovery from oilsands ore comprises contacting the oil sands ore containing bitumen withan aqueous solution comprising at least one C₁-C₇ monocarboxylate saltor acid.

In another embodiment, the process comprises mixing oil sands ore with afirst aqueous solution to form a slurry; aerating the slurry to form afroth containing bitumen within the slurry; separating the froth fromthe slurry; adding a second aqueous solution comprising at least oneC₁-C₇ monocarboxylate salt and/or acid, wherein adding the secondsolution is prior to or during one or more of the preceding steps; andisolating bitumen from the froth.

The disclosure may be understood more readily by reference to thefollowing detailed description of the various features of the disclosureand the examples included therein.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures wherein the like elements are numberedalike:

FIGS. 1-3 pictorially illustrate, after mixing, a separation flask of acontrol sample that contained toluene and aqueous bitumen foam, a samplecontaining 5% potassium formate by weight of the bitumen foam, and asample containing 50% potassium formate by weight of the bitumen foam,respectively.

DETAILED DESCRIPTION

Disclosed herein are processes for separating trapped and bound bitumenfrom oil sands. The process generally includes adding at least onecarboxylate salt and/or acid during a bitumen separation process and inan amount effective to lower interfacial surface tension. The processfor separating the trapped and bound bitumen from oil sands isapplicable to both surface mining and in situ mining techniques. In oneembodiment, the carboxylate salt and/or acid is a C₁-C₇ alkyl, and C₁-C₂alkyl in other embodiments. In another embodiment, the carboxylate saltand/or acid is a monocarboxylate salt and/or acid. Exemplary carboxylatesalts include, without limitation, formates, acetates, and mixturesthereof. The cation is not intended to be limited and can be sodium,potassium, cesium, ammonium, and the like. Advantageously, the additionof the carboxylate salts and/or acids as defined above increasesseparation efficiency and reduces energy consumption by loweringviscosity of the separated oil, thus lowering pumping costs as well asincreasing the pipeline capacity of the oil sands pipeline. In addition,the inventive composition can eliminate the use of caustics such assodium hydroxide, which represents a significant commercial advantage.

The at least one carboxylate salt and/or acid can be added prior toand/or during the bitumen extraction process. In one embodiment, the atleast one carboxylate salt and/or acid is added during the conditioningstep of a hot water process for extracting bitumen. By way of example,the carboxylate salt and/or acid is added to an aqueous solution withhot water at a temperature within a range of about 40° C. to about 90°C. to condition the oil sand ore for quick release of the bitumen.Alternatively, the aqueous solution containing the carboxylate saltand/or acid can be vigorously mixed with the oil sands in the largetumblers or conditioning drums or an extraction pipeline without theaddition of hot water. That is, the aqueous solution containing thecarboxylate salt and/or acid can be added directly to the oil sand or toan oil sand water mixture, wherein the conditioning step can be free ofa heating step, thereby providing significant energy savings. In stillother embodiments, the process temperature of a slurry based extractionprocess is between about 0° C. and 60° C. to which the carboxylate saltand/or acid can be added.

It has been discovered that the aqueous solution containing thecarboxylate salt and/or acid efficiently breaks the large lumps of theoil sands to form the slurry. Conditioning in this manner can be with orwithout the addition of an aqueous base such as sodium hydroxide. As isknown in the art, sodium hydroxide is typically added to the froth todisperse the oil sands and reduces the viscosity of the slurry. However,the addition of sodium hydroxide adds expense to the process. Moreover,the middling phase is substantially non-transparent due to thesignificant amounts of sand and bitumen retained therein. Applicantshave discovered that the addition of the carboxylate acid and/or saltsof the present disclosure to the slurry (without caustic, e.g., sodiumhydroxide) qualitatively resulted in a significantly lesser amount ofsand remaining in the middling phase. The treated slurry with thecarboxylate salt and/or acid (without the addition of sodium hydroxide)has been found to settle immediately upon resting to provide asubstantially clear middling phase. In contrast to froth treatment withsodium hydroxide, the froth with the carboxylate salt and/or acid willsettle to a greater degree than with caustic to form a sediment layerand supernatant water in a shorter period of time. Moreover,significantly less foam appears to have been formed.

The aqueous solution containing the at least one carboxylate salt and/oracid can have a concentration of 1 to 75 weight percent. In otherembodiments, the aqueous solution containing the carboxylate salt and/oracid can have a concentration of 5 to 50 weight percent. Any source ofwater can be used to form the aqueous solution containing thecarboxylate salt or acid. If used in conjunction with the hot waterprocess, the carboxylate salt and/or acid can be added to the hot wateras a solid in an amount effective to provide a concentration of 1 to 75weight percent, and 5 to 50 weight percent in other embodiments.

Once extraction of bitumen has taken place, the aqueous solutioncontaining the carboxylate salt or acid can be sent to the tailingspond. In surface mining the oil sands, the aqueous solution containingthe carboxylate salt and/or acid can be recycled.

The composition may further include an additive such as a surfactant, ananti-foaming agent, a polymer, a flocculent, a mineral oil or a mixturethereof. In one embodiment, the additives are in an amount of 0.01 to 10weight percent based on a total weight of the composition.

In order that the disclosure may be more readily understood, referenceis made to the following examples, which are intended to illustrate theinvention, but not limit the scope thereof.

Example 1

In this example, extraction of bitumen from bitumen foam was examined asa function of potassium formate concentration.

In a separation flask, three samples of toluene and aqueous bitumen foamwith and without different concentrations of an aqueous potassiumformate solution were vigorously mixed. A control sample contained nopotassium formate was compared to samples containing 5% (wt/wt)potassium formate aqueous solution and at 50% (wt/wt) potassium formateaqueous solution. As shown in FIGS. 1-2, the samples containing thepotassium formate solution visibly provided significantly improved phaseseparation when compared to the sample that did not include thecarboxylate additive as shown in FIG. 3.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. The patentable scope of the inventionis defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they have structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

1. A composition for enhancing the efficiency of bitumen recovery fromoil sands ore, comprising: at least one C₁-C₇ monocarboxylic acid saltand/or acid in an aqueous liquid carrier; and oil sands ore containingbitumen, wherein the at least one C₁-C₇ monocarboxylic acid salt and/oracid is in an amount effective to separate the oil sands into a frothphase, a middling phase, and sand and rock phase.
 2. The composition ofclaim 1, wherein the C₁-C₇ monocarboxylic salt is potassium formate,sodium formate, cesium formate, ammonium formate, or a mixture thereof.3. The composition of claim 1, wherein the C₁-C₇ monocarboxylic saltand/or acid is in an amount of 1 to 75 weight percent based on a totalweight of the composition.
 4. The composition of claim 1, wherein theC₁-C₇ monocarboxylic salt and/or acid is in an amount of 5 to 50 weightpercent based on a total weight of the composition.
 5. The compositionof claim 1, further comprising an additive in an amount of 0.01 to 10weight percent based on a total weight of the composition, wherein theadditive is a surfactant, an anti-foaming agent, a polymer, aflocculant, a mineral oil or a mixture thereof.
 6. A process forenhancing the efficiency of bitumen recovery from oil sands ore,comprising: contacting the oil sands ore containing bitumen with anaqueous solution comprising at least one C₁-C₇ monocarboxylate saltand/or acid.
 7. The process of claim 6, wherein contacting the oil sandore with the aqueous solution is at a temperature of 0° C. to 60° C. 8.The process of claim 6, wherein the C₁-C₇ monocarboxylic salt ispotassium formate, sodium formate, cesium formate, ammonium formate, ora mixture
 9. The process of claim 6, further comprising adding anadditive to the aqueous solution in an amount of 0.01 to 10 weightpercent based on a total weight of the solution, wherein the additive isa surfactant, an anti-foaming agent, a polymer, a flocculant, a mineraloil, or a mixture thereof.
 10. The process of claim 6, wherein the oilsand is surface mined and the process further comprises recycling theaqueous solution.
 11. The process of claim 6, wherein the process isfree of a heating step.
 12. The process of claim 6, wherein the oilsands ore containing the bitumen is a froth.
 13. The process of claim 6,wherein the at least one C₁-C₇ monocarboxylic salt and/or acid is in anamount of 1 to 75 weight percent based on a total weight of the aqueoussolution.
 14. A process for extracting bitumen from an oil sand,comprising: mixing oil sands ore with a first aqueous solution to form aslurry; aerating the slurry to form a froth containing bitumen withinthe slurry; separating the froth from the slurry; adding a secondaqueous solution comprising at least one C₁-C₇ monocarboxylate saltand/or acid, wherein adding the second solution is prior to or duringone or more of the preceding steps; and isolating bitumen from thefroth.
 15. The process of claim 14, wherein the C₁-C₇ monocarboxylicsalt is potassium formate, sodium formate, cesium formate, ammoniumformate, or a mixture thereof.
 16. The process of claim 14, wherein theC₁-C₇ monocarboxylic salt and/or acid is in an amount of 1 to 70 weightpercent based on a total weight of the composition.
 17. The process ofclaim 14, wherein isolating the bitumen comprises heating the froth inan amount effective to substantially deaerate the froth; and addingnaptha to the deaerated froth.
 18. The process of claim 14, wherein thefirst aqueous solution comprises hot water at a temperature of about 40°C. to about 90° C.
 19. The process of claim 14, wherein the firstaqueous solution comprises hot water at a temperature of about 0° C. toabout 60° C.